Abrasive tool



June 22, 1965 INVENTOR. EDI M4190 A ZUZELO N HSW United States Patent 3,196,045 AERASIVE TQOL Edward A. Zuzelo, 828 Suburban Station Bldg, Narberth, Pa. Filed Dec. 4, 1963, Ser. No. 327,932 3 Claims. (Cl. 51-4209) This invention relates to abrasive tools, such as are useful for abrading a work surface to grind or polish it, and particularly such tools for working in square corners.

Disc-shaped abrasive wheels are well known tools for grinding or polishing metal, stone, and other materials. Such tools conventionally are used by presenting either the peripheral edge or one face to the'rotating wheel to the work. Also known are dished or offset abrasive wheels, which have a raised or depressed hub or center portion; they present only a relatively narrow abrading surface regardless of their orientation to the work. Except when most skillfully used an abrasive Wheel is conductive to areuate scoring of the work surface, because of uninterrupted contact of the work surface with the wheel rim, and this difficulty often is aggravated by excessive abrasion caused by fragments worn from the work or the wheel and trapped therebetween. It is especially difiicult to produce uniform results by means of conventional tools when working on the inside of square corners.

A primary object of the present invention is provision of rotary abrasive tool means useful in grinding or polishing surfaces bounded by square corners.

Another object is formation of a dished or offset rotary abrasive tool non-conductive to scoring of the work surface.

A further object is production of a rotary abrasive tool adapted to expose a peripheral portion of the work surface while it is being abraded with the tool.

Other objects of this invention, together with means and methods for attaining the various objects will be apparent from the following description and the accompanying diagrams.

FIG. 1 is a plan of a rotary abrasive tool according to the present invention;

FIG. 2 is a side elevation, partly in section, of the abrasive tool of FIG. 1;

FIG. 3 is an enlarged sectional elevation of a portion of a wall construction useful in such an abrasive tool;

FIG. 4 is a sectional elevation of another wall construction useful in such abrasive tools;

FIG. 5 is an elevation of abrasive tool means embodying the tool of preceding views in use position on a floor along an adjacent wall;

FIG. 6 is a plan corresponding to the preceding view, showing the abrasive tool in use position on the floor in a corner defined by two adjacent walls intersecting at a right angle.

In general, the objects of the present invention are accomplished by means of a dished, generally tetrahedral abrasive tool having an open base and three somewhat convex sides identical to one another. More particularly the tool is shaped such that any intersecting plane parallel to the base defines thereon an equilateral triangle having each side curved in the form of an are centered on the opposing vertex. The invention contemplates use of such a tool in conjunction with drive means for rotating the tool about its axis and simultaneously moving the shaft eccentrically (moving the axis through a sequence of parallel locations) so that the rotating tool sweeps out on a fixed square on a work surface.

FIG. 1 shows in plan view rotary abrasive tool 10, which is exemplary of the present invention. It has round hub 13 with central bore 19 through it. Three identical lateral faces 11, 12, and 1.3 surround the hub and terminate in arcuate peripheral edges, each centered on (i.e., constructed about, in a geometrical sense) the vertex at which the peripheral edges of the other two sides meet one another.

FIG. 2 shows the abrasive tool of FIG. 1 from the side, with lateral face 13 partly cut away to reveal a portion of the hollow interior 15. Part of the wall underlying the cut away portion of lateral face 13 appears in section. Base 14 ofthe tool is seen to the flat.

FIG. 3 shows, in greater sectional detail than in FIG. 2, a wall construction suitable for the abrasive tools of this invention. Here outer and inner facing layers 27 and 29 sandwich central layer 28 of the wall.

FIG. 4 shows in similar section another wall construction suitable for abrasive tools constructed according to the present invention. Here, the tool wall has outer and inner facing layers 35 and 39 on its opposite sides and has intermediate reinforcing layer37. Abrasive layers 36 and 38 of the wall are flanked on one side by the intermediate layer 37 and on the other side by one of the facing layers.

The composition of the facing layers and (in the instance of the construction shown in FIG. 4) of the central layer of the wall may be paper, textile fabric (often glass), or wire fabric or mesh, for example. Paper may function during manufacture to support or confine the abrasive material, as may be important in certain stages of manufacture, while the other mentioned compositions serve also to reinforce the structure of the manufactured tool itself. With well bonded abrasive material either (or both) of. the facing layers may become less important or even unnecessary and accordingly may be omitted.

The inner layer or layers of the wall, containing the abrasive itself, usually will be bonded by a thermosetting resin, such as phenol-formaldehyde or urea-formaldehyde, or by rubber or other polymerizable or similarly hardenable material capable of bonding the finely divided abrasive particles together and adhering to an adjacent facing or reinforcing layer, which normally will become embedded therein or impregnated therewith. The abrasive itself may be silicon carbide, aluminum oxide, or other sufiiciently hard material.

It is customary and well known in the art to mix the resin or other binder in more or less granular form with the (usually smaller) abrasive particles in the presence of a liquid, which may also be a softening agent or solvent for the resin material, adapted to wet both components so that the resin granules become coated with the abrasive particles. Subsequent heating, usually with application pf pressure, bonds the components together.

FIGS. 5 and 6 show in side elevation and plan, respectively, tool 10) and auxiliary mechanism in position for grinding or polishing a floor surface in a rectangular corner of a room or the like. Motor 41, which has handles 42 and 43 extending at right angles to one another from the left side and rear of the body thereof, has rotary shaft 44 extending downward therefrom near the front. Fullfioating chuck 45 is interposed between that shaft and tool shaft 46, which extends from the chuck to hub 18, where it is affixed to the tool.

The tool rests at its base on floor 51 touching wall 52 (FIG. 5) and wall 53 (FIGS. 5 and 6), which mutually intersect perpendicularly to one another. In FIG. 6 the surface of floor 51 is divided into two portions: 51r, which is shown stippled to indicate that it is rough, and 51s, shown clear to indicate that it has been smoothed by the abrasive tool. Portion 51s is seen to have a square outline (with only very slightly rounded corners).

Full-floating chucks adaptable to the present purpose are well known, one type having been developed early in this century by Watts (Pat. 1,241,175 and others), and

no illustration is included here. Most convenient for the present purpose is a chuck having a guide piece (square) integrally formed with or otherwise retained in the fixed housing of the chuck and surrounding a close-fitting shank portion of the tool shaft shaped like the tool outline (and proportionately smaller) It is a characteristic of such a chuck that, as the motor shaft turns about any fixed axis, the chuck moves shaft 46 laterally (while maintaining its axis always parallel to its other axial positions) and rotates it and the attached tool to accomplish the desired result. Reduction gearing may be included so that the tool will rotate more slowly than the motor shaft speed.

As can be seen, the peripheral portion of the surface being ground or polished by the tool is exposed intermittently during rotation so that the degree of treatment is readily visible. Of course, a portion (concealed by the tool in FIG. 6) of the surface inside square portion 51s is not treated at any given location of the motor shaft axis, but the entire assembly may be moved laterally to sweep out that portion, or it may be treated by a conventional grinding wheel.

The abrasive tools of this invention may be produced from suitable materials, such as those already'mentioned, by conventional laminating, molding, or similar operations. Advantages inherent in the use of these dished abrasive tools have been pointed out above. Their use in or near square corners leads to improved workmanship and lower working costs than obtained there with circular abrasive wheels or other conventional grinding or polishing tools. Further benefits of this invention will become apparent and accrue to those persons undertaking to praetice it.

The claimed invention:

1. Dished abrasive tool open at its base and shaped 41:. such that any intersecting plane parallel to the base defines thereon an equilateral triangle having each side curved in an arc centered on the opposing vertex.

2. Rotary abrasive tool comprising a hollow article having a hub, an open base, and identical lateral surfaces, each of the lateral surfaces having three side edges and being bounded on two of the three side edges by the other two lateral surfaces, the boundaries extending similarly to one another outward and downward from the hub, and by a third side edge extending from one to the other of the boundaries at their outer ends in'the configuration of an arc inscribed in the plane containing the ends of the three boundaries and centered on the outer end of the other of the three boundaries.

3. Rotary abrasive tool open at its base and hollow inside, having three identical generally triangular lateral wall segments of constant thickness including reinforcing fabric and abrasive particles bonded thereto, each of the Walls being bounded on each of its two side edges by one of the other wall segments and having its third edge free, the free edges of the three segments being mutually coplanar and, bounding the open base of the tool, each of the free edges being, when viewed along a line of sight perpendicular to the base, arcuate and centered on the vertex at whichthe free edges of the other two wall segments join.

References Cited by the Examiner UNITED STATES PATENTS 881,627 3/98 Rowland et al 5l-209 2,997,820 8/61 Skoog 51209 LESTER M. SWINGLE, Primary Examiner. 

1. DISHED ABRASIVE TOOL OPEN AT ITS BASE AND SHAPED SUCH THAT ANY INTERSECTING PLANE PARALLEL TO THE BASE DEFINES THEREON AN EQUILATERAL TRIANGLE HAVING EACH SIDE CURVED IN AN ARC CENTERED ON THE OPPOSING VERTEX. 